The present invention relates to a gas mixing apparatus adapted to generate a continuous gas mixture flow consisting of a main stream of a carrier gas to which one or more gas components are added in measured quantities.
The continuous gas stream is generated with exactly defined components with very high accuracy and very short adjustment periods.
Gas mixing apparatus utilizing diaphragms with various apertures have been utilized; but they permit only stepwise adjustment of the gas mixture composition. They also generate large amounts of excess gases. Also gas mixing apparatus with thermal mass flow regulators have become known. However, the accuracy of the thermal mass flow regulators depends greatly on the temperature of the environment in which they are utilized. Wall effects and particularly dead volumes cause delay effects during changes in concentration, that is, during changes of the compositions of the gas stream.
It is the principal object of the present invention to provide a gas mixing apparatus in which the composition of the gas is infinitely variable, in which only small amounts of excess gas are generated and in which the dead volumes present in the mixing control elements are very small.